In JP11-280801 A (Japanese Laid Open Publication No. Hei 11-280801), there is a description that, in order to “prevent in advance a degradation in braking characteristic, generation of vibrations, and a degradation in assembly property caused by an imbalance in the weight of a carrier, thereby increasing durability and reliability”, “a pin slide mechanism is constructed as follows: a pair of support portions are provided to a carrier fixed to a non-rotation portion of a vehicle; one of the support portions is provided at a distal end of an arm portion extending from the carrier to an inner side of the vehicle; and cylinder portions provided on both sides of a caliper main body are fitted via sleeves into pin portions of pin bolts that bridge between both the support portions and are tightened and fixed to the support portions from an outer side of the vehicle”.
Further, in JP 11-280801 A, there is a description that “the caliper that is heavy due to the inclusion of the electric power device is supported by the both support portions stably in a manner of a double-support beam, thereby preventing an inclination of the caliper upon the braking, suppressing an increase in drag torque and a degradation in judder characteristic, and suppressing the generation of a vibration due to a pin clearance in the pin slide mechanism”.
Referring to FIG. 11, a description is now given of a problem relating to a vibration caused by road surface irregularities when the vehicle is traveling. A case in which a beam X is supported by a member Y at points P1 and P2, and a vibration of an amplitude A is input from a point P0 is assumed. A portion between the points P1 and P2, which are the support points, forms a double-support beam, and hence the amplitude of a vibration is unlikely to be amplified at this portion. On the other hand, a point P3 or a point P4, which is an end point of the beam X, forms a cantilever, and hence the vibration may be amplified. Moreover, an increase amount of the amplitude increases as a distance from the support point increases. For example, the amplitude tends to be amplified more at the point P4 (distance L4 from the support point P2) than at the point P3 (distance L3 from the support point P1, which is shorter than the distance L4). As a result of the amplification of the amplitude, an acceleration acting on each position increases, and an excessive inertia thus acts on a member arranged at a place at which the amplitude amplification tends to occur.
It is important for an electric braking device arranged on a wheel side to appropriately balance the weight as well as to decrease a dimension (length) in an axial direction, thereby suppressing the amplitude of the device caused by the vibration input from the road surface. Further, in the device, sensitivity to the influence of the vibration depends on the component, and it is thus also important to arrange the components in consideration of components that are more sensitive to the influence of the vibration.